From 156af3ac98da24f0155eed18ec546157436d6b2e Mon Sep 17 00:00:00 2001 From: "Denis V. Lunev" Date: Wed, 17 Aug 2016 21:06:54 +0300 Subject: block: fix possible reorder of flush operations This patch reduce CPU usage of flush operations a bit. When we have one flush completed we should kick only next operation. We should not start all pending operations in the hope that they will go back to wait on wait_queue. Also there is a technical possibility that requests will get reordered with the previous approach. After wakeup all requests are removed from the wait queue. They become active and they are processed one-by-one adding to the wait queue in the same order. Though new flush can arrive while all requests are not put into the queue. Signed-off-by: Denis V. Lunev Tested-by: Evgeny Yakovlev Signed-off-by: Evgeny Yakovlev Message-id: 1471457214-3994-3-git-send-email-den@openvz.org CC: Stefan Hajnoczi CC: Fam Zheng CC: Kevin Wolf CC: Max Reitz Signed-off-by: Stefan Hajnoczi --- block/io.c | 3 ++- 1 file changed, 2 insertions(+), 1 deletion(-) (limited to 'block') diff --git a/block/io.c b/block/io.c index 9c04086286..420944d80d 100644 --- a/block/io.c +++ b/block/io.c @@ -2358,7 +2358,8 @@ out: /* Notify any pending flushes that we have completed */ bs->flushed_gen = current_gen; bs->active_flush_req = NULL; - qemu_co_queue_restart_all(&bs->flush_queue); + /* Return value is ignored - it's ok if wait queue is empty */ + qemu_co_queue_next(&bs->flush_queue); tracked_request_end(&req); return ret; -- cgit v1.2.3